There are plenty of vendors that specialize in this area. In order to pick one best suited, you must consider more than "chemical injection" and "24gal/day".
What type chemical? Corrosive? Solids? temperature concerns? How much pressure: 1,000 psi or 10,000 psi?? Is this service in the oilpatch, possibly requiring API 674 or 675?? So many questions, so little info.....
You might start looking at Milton-Roy, Lewa, Danfoss if they are API services.